Investigations into alleged vehicle fraud at the Dunedin City Council Citifleet/Citipark unit have unravelled a vast network of vehicle transactions over the past 11 years, an informed source has told Stuff.

The probe has been under way for more than a month. Accountancy firm Deloitte was commissioned to investigate whether dozens of Dunedin City Council fleet vehicles had been sold and the proceeds pocketed.

The investigation was sparked when discrepancies appeared in the number of fleet vehicles recorded by the council's fleet unit Citifleet/Citipark.

Stuff has been told this week the council gave Deloitte investigators a list of council vehicle movements through a network of buyers and subsequent owners over the 11 years.

It included buyers of the vehicles, who now owned the vehicles, and how long they had owned them.

At least three people, who took ownership of many vehicles, are among those in a network under suspicion of being involved in the fraudulent activity.

Council chief executive Sue Bidrose indicated in media releases on the matter, the council was treating the matter as a fraud investigation. It has not named anyone in connection with the alleged activity.

Stuff understands Citifleet/Citipark manager Brent Bachop, who died on May 21 in a suspected suicide, was allegedly among the network of buyers.

It is understood Bachop had been told that discrepancies had been found in vehicle numbers within his unit.

Bachop had worked in the unit for more than 20 years, the past 10 or so as manager.

Bidrose today declined to give reasons for why she believed the alleged fraudulent activity now coming to light had been allowed to go on for so long without detection.

She declined to give details of checks and balances that existed within the Citifleet unit, and declined to comment on an unsuccessful inquiry into the same matter two years ago.

Stuff has been told the council's former chief executive, Paul Orders, investigated concerns about possible fraud within Citifleet/Citipark raised by Dunedin City councillor Lee Vandervis and found nothing untoward.

"While the Deloitte investigation is ongoing it is not appropriate to answer specific questions relating to Citifleet activities," Bidrose said.

Questions are also being raised as to why police are not involved in the investigation.

Dunedin CIB confirmed this afternoon it was not investigating.

Bidrose said police were "aware of the situation".

"But the DCC will need to have evidence of wrongdoing and then it would refer those issues to the police," she said.

In a blog to staff this week Bidrose indicated the council was looking at a major fraud inquiry, with the Citifleet/Citipark investigation. It was expected to reflect negatively on its financial management and could dent ratepayer trust.

The investigation has shocked those in the Dunedin car retail, automotive, and enthusiast community, especially those who knew Bachop personally.

One of Bachop's close friends, Mike Wilson, said he remembered Bachop as a kind and humble family man, who enjoyed mountainbiking and keeping fit and was a dedicated president of Dunedin car club Conrodders.